Process for printing with sulphuric esters of leuco vat dyestuffs



Patented June 28, 1949 PROCESS FOR PRINTING: WITH SULPHURIG ESTERS FLEUCO VAT DYESTUFFS William B. Hardy and Elizabeth M. Hardy, BoundBrook, N. J., assignors to American Cyanamid Company, New York, N. Y., acorporation of Maine No Drawing. Application July 31,1946, Serial N0.687,520

7 Claims.

This invention relates to an improved process for printing textilefibers and fabrics with diflicultly oxidizable sulfuric ester salts ofleuco vat dyes using the dichromate-acid vapor developing method.

Printing of textiles with sulfuric ester salts of leuco vat dyes hasbeen carried out by two general procedures. One of the processesincorporates a powerful oxidizing agent in the printing paste, such as achlorate, and the print is developed by treatment with steam and. acidvapors. This process is generally usable with all stable dyestuffs.However, it is open to a very serious disadvantage when the dye mixtureprinted contains dyes which are sensitive to oxidizing agents. In theprocess such colors are rather severely attacked and the use ofprocesses involvingstrong oxidizing agents such as chlorates have,therefore, been definitely limited in their field of utility.

Some of the disadvantages of the chlorate acid vapor process areovercome by a procedure in which a milder oxidizing agent, such as adichromate, is incorporated into the printing paste containing sulfuricesters of leuco vat dyestuffs, and aging effected with. acid vapors,such as, for example, mixed acetic acid-formic acid vapors. It is withthis dichromate process that the improvement of the present inventiondeals.

The dichromate-acid vapor process, while it does not attack sensitivedyes, is also subject to a number of drawbacks. The principal one isthat certain. sulfuric esters of leuco vat dyestuffs which aredifii'cultly oxidizable .do not fully develop during the acid vaportreatment within the usual aging periods of about 1-5 minutes, even whenlarge excesses of the oxidizing agent are used. Also, drastic increasesin the aging timete. g., up to 20 minutes, do not bring aboutfulldevelopment. A further drawback: is that development. of theincompletely developed color sometimes continues slowly duringafter-storage of the fabric which results in a change of shade. As aresult of the above drawbacks the dichromate-acid vapor process has beenrestricted to result the dichromate-a-cid vapor process has not.

been usable with a certain class of sulfuric estersof leuco vat dyes,including. some of the import:- ant vat colors.

According to the: present inventionit. has been,

' able sulfuric esters of leuco vat dyestuffs.

found that full deveIopmen-t in a short time is obtained by thedibh-romate-acid vapor process regardless of whether this radical isattached to hydrogen to form'- the free acid or toa basic radical toform a salt, the term aniline sulfonic acid radical" will be used intheclaims to cover either type" of compound, and it will be used therein inno other sense.

The substituent in the aniline sulfonic acid is an aliphatic hydrocarbonradical having not more than one double bond. There may be present onesubstituent or a plurality. The sulfonic acids which may be consideredas development accelerators or catalysts may be added either to theprinting paste or tothe dry ester salts used in preparing aprintingformula. When properly used, fast prints are obtained of excellentstrength and brilliance, the dyeing strength being increased inmanycases from values as low as 10% to substantially the full color value.

Improved results of the present invention are obtained regardless ofwhether the alkyl or alkenyl group orgroups are attached to a carbonatom of the benzene ring or to the nitrogen atom. This is unusualbecause ordinarily the presence of an alkyl'or alkenyl group produceschemical compounds of quite different characteristics, dependingonwhether it is a ring substituent or is attached. to the nitrogen. It isnot known why the contrary is the case in the process and compositionsof the present invention, and it is not desiredto limit the same to anytheory. Among the typical compounds included in the present inventionare sulfonic acids of toluidines, xylidines, cumid'ines, cymi'dines andN-mono and dialkyl or alkenyl anilines, such as diethylaniline,.diallylaniline, and the like. The position. of the sulfonic acid doesnot appear to be vital.

. There is some variation in degree of positive results obtained withindividual members of the substituted aniline sulfonic acids of thepresent invention, but the. class as a whole gives useful improvementsin printing with difficultly oxidiz- It is an advantageof the presentinvention that the added compounds do not themselves form disturbing.oxidationcolors under the conditions of operation.

The improved results which are obtainable with the printing assistantsof the present invention appear to be quite specific to the class.Normally, the chemical behavior of alkyl substituted compounds andaralkyl substituted compounds is quite similar. In the present case thisdoes not hold true and sulfonic acids of N-lbenzyl anilines do not showthe great improvement which is typical of the compounds of the presentinvention. The underlying chemical reason for this sharp difference isnot as yet proven, and no theory is advanced why such closely relatedaralkyl derivatives do not possess the valuable properties of theassistants of the present invention.

The properties of an oxidation accelerator or catalyst, which are somarked in the substituted aniline sulfonic acids of the presentinvention, are quite surprising because the same general type ofcompound has been used in processes of printing with other and strongeroxidizing agents, such as chlorates. In such a process the compoundsexert the opposite effect and prevent over-oxidation, particularly whenused in a process in which development is effected by steaming and notby acid vapors. The reasons for the contrary effects in the differentprocesses are likewise not known.

It should be emphasized that the process of the present invention isstrictly limited to an improved dichromate-acid vapor printing processin which leuco vat dye ester salts are used which are diificultlyoxidizable in this process. It should not be confused with processes inwhich develop ment is efiected by passing the printed goods through aliquid bath containing an oxidizing agent, such as nitrite ordichromate. In general, vat dye ester salts which are difficult tooxidize by this bath process are also difficult to oxidize by thedichromate-acid vapor process.

There are, however, a few exceptions where a leuco vat dye ester salt isfairly readily oxidized by the bath process and is difiiculty oxidizableby the dichromate-acid vapor process, requiring one of our catalysts forfull development.

It is an advantage of the present invention that the amount of oxidationaccelerator or dyeing assistant is not critical. Apparently, thecompound does not take part strictly as a reactant, and a considerablysmaller amount of the accelerator may be used than oxidizing agent. Ingeneral an amount of accelerator which is somewhat less than the weightof the dyestuff ester gives best results. However, good results areobtained from quite a wide range of proportions. It is, of course,necessary to add suflicient accelerator to produce rapid oxidation, theminimum amount varying with different accelerators and with difierentdyes. Small traces of accelerator are, of course, not effective, as thereaction appears not to be a purely catalytic one in which minutequantities of accelerator are capable of carrying on the reaction ofvery large amounts of dyestufi and oxidizer.

It is an advantage of the present invention that the prints are not onlyof excellent strength and brilliance, the strength being increased inmany cases from as low as to substantially full color value, but thatthe process is controllable, that is to say, the rate of development canbe influenced by the addition of varying amounts of accelerator. Thus,prints can be made to develop in a shorter time than normal, forexample, in a few minutes, or the color development may be caused toproceed more slowly so that the reaction rate can be controlled withinwide limits, in accordance with the desire of the operator. In everycase prints are obtained which show improved levelness and freedom fromspecks, and they do not show any deterioration in shade due to afterdevelopment. It is a further advantage of the invention that theaccelorator permits operation without a larger excess of oxidizingagent.

The invention will be described in greater de tail in conjunction withthe following examples, which are typical. The parts are by weight.

Example 1 7 parts of the sodium salt of the disulfuric acid ester ofleuco tetrabrornoindigo (equivalent to 4.35 parts of tetrabromoindigo)are blended with 2 parts of 2-amino, 3-5-dimethylbenzene sulfonic acid(Na salt) and 1.1 parts of sucrose to give a powder containingapproximately 43% real dye.

A. printing paste is made from this blended powder, using the followingingredients:

Parts Color 3 Urea 6 A mixture of 4 parts acetamide, 4 parts diethyleneglycol and 2 parts furfuryl alcohol 3 Water 11 A 15% gum paste in waterAmmonium chloride .75 25% ammonia 2.0 Sodium dichromate 5.0

The cloth is printed with this paste and the resulting prints are agedin formic and acetic acid vapors. The prints develop to substantiallyfull color value, in 1 to 3 minutes. If no metaxylidine sulfonic acid ispresent in the powder, only 10-15% of the expected color value isobtained even after as long as 10 minutes aging.

Example 2 7 parts of the crude sodium salt of the disulfuric ester ofleuco tetrabromoindigo (equivalent to 4.35 parts of tetrabromoindigo)are blended with 2 parts of sodium 2-amino-5-methylbenzene sulfonate and1.1 parts of sucrose to give a powder containing approximately 43% realdye. When this powder is incorporated into a printing paste as describedin Example 1, printed and aged, prints of substantially full color valuewere obtained. In the absence of the sodium paminotoluene sulfonate onlyabout 10% of the expected color value is obtained.

Example 3 6 parts of crude sodium salt of the disulfuric ester of leucotetrabromoindigo (equivalent to 3.59 parts of tetrabromoindigo) wereblended with 2 parts of sodium N,N-diethylaniline 4- sulfonate and 0.28part of sucrose to give a powder of approximately 43% dye content.Prints obtained from this product by the usual procedure of printing anddyeing described in Example 1, develop to full color value on shortaging. Only a small fraction (about 10%) of the desired color value canbe obtained in the absence of sodium diethylaniline sulfonate.

i odi-nn diethylaniline sulfonate also greatly increases the printingstrength of the blended powder of the sodium salt of the disulfuricester of leuco 7,7-dimethyl 5,5 dichlorothioindigo over that of asimilar powder containing no sodium diethylaniline sulfonate.

Example 4 ample 1, gives prints of essentially full strength on shortaging. The required. color value is. not obtained under identicalconditions in the absence of sodium diallylaniline sulfonate.

Example 5 7 parts of the sodium salt of the disulfuric acid ester ofleuco 7,7-dimethyl-5,5-dichlorothioindigo (containing 3.9 parts of7,7'-dimethyl- 5,5'-dichlorothioindigo) are blended with 1.66 parts of2-amino 3,5-dimethylbenzene sulfonic acid sodium salt to give a powderof approximately 44% real dye content. Prints obtained from this powderby the procedure described in Example 1 develop to substantially fullcolor value on 1 to 3 minutes aging. In the absence of the meta-xylidinesulfonic acid sodium salt, only to 20% of the expected color value isobtained after 10 minutes aging.

If the meta-xylidine sulfonic acid sodium salt in the above example isreplaced by the sodium salt of N-benzyl sulfanilic acid only about 20%of the expected color value is obtained after 10 minutes aging.

Example 6 9 parts of the sodium salt of the disulfuric acid ester ofleuco 4,5,4',5-dibenzthioindigo (containing 4.67 parts of real4,5,4,5-dibenzthioindigo) are blended with 1.38 parts 2-amino3,5-dimethylbenzene sulfonic acid sodium salt to give a powdercontaining approximately 45% real dye. Prints of substantially fullcolor value are obtained from this powder by means of the previouslydescribed printing formula and in an aging time of 1 to 3 minutes. If nometa-xylidine sulfonic acid sodium salt is included in the powder, only10 to 20% of the expected color value is obtained even after a 10 minuteaging.

The leuco vat dye ester salt used in this example constitutes one of thefew exceptions referred to in the introductory portion of thespecification. This ester salt has been characterized in the literatureas being fairly readily oxidizable in liquid development processes wherethe leuco ester salt is used primarily for dyeing rather than printing.In the dichromate-acid vapor process of developing prints this leucoester salt is to be characterized as difficultly oxidizable since itwill not develop to full color value in a reasonable time without theuse of the accelerators of the present invention.

Example 7 4.7 parts of the sodium salt of the disulfuric ester of leuco4,4-dimethyl-6,6-dichlorothioindigo (containing 2.55 parts of real dye)are blended with 1.05 parts of Z-amino 3,5-dimethylbenzene sulfonic acidsodium salt and 1.54 parts of sucrose to give a powder containing 36%real dye. Prints obtained from this product by the procedure describedin Example 1 give essentially the full color value on aging for 1 to 3minutes. In the absence of the meta-xylidine sulfonic acid, only a 5% to10% of the expected color value is obtained even after 10 minutes aging.

We claim:

1. A process for printing difficultly oxidizable sulfuric ester salts ofleuco vat dyestuffs of the indigoid type which comprises printing theester salts with dichromates and in the presence of an efiective amountof an aniline sulfonic acid radical, substituted by at least onealiphatic hydrocarbon radical containing not more than one double bond,and developing the print with acid vapors.

2. A process according to claim 1 in which the substituted anilinesulfonic acid is 2-amino-3,5- dimethylbenzene sulfonic acid.

3. A process according to claim 1 in which the substituted anilinesulfonic acid is N,N-diethylaniline-para-sulfonic acid.

4. A process according to claim. 1 in which the substituted anilinesulfonic acid is a paratoluidine sulfonic acid. V

5. A process according to claim 1 in which the sulfuric ester salt isthe disulfuric ester salt of leuco tetrabromoindigo.

6. A process according to claim 1 in which the sulfuric ester salt isthe disulfuric ester salt of a dimethyl-dichlorothioindigo.

'7. A process according to claim 1 in which the sulfuric ester salt isthe disulfuric ester salt of leuco 4,5,4',5'-dibenzthioindigo.

WILLIAM B. HARDY. ELIZABETH M. HARDY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 1,779,305 Brandt Oct. 21, 1930!2,234,301 Niederhausern Mar. 11, 1941 FOREIGN PATENTS Number CountryDate 398,571 France Mar. 26, 1909

